Organic phenolic phosphites are known for their antioxidant properties when added to polymers and other organic materials. See Plastics Additives Handbook, 4th Ed. R. Gaechter and H. Mueller Editors, 1993. One such example is tris(nonylphenyl)phosphite (“TNPP”),
a phosphite additive derived from nonylphenol. It is typically a mixture of ring and chain isomers of C9H19C6H4OH, which has been used for years to stabilize polymers, especially synthetic rubber and polyethylene products against oxidation and color degradation.
Organic alkylphenolic phosphites in general, are good secondary antioxidants, but there is a perceived problem that has developed in the scientific community that a number of commonly used compounds, including nonylphenol, may exhibit estrogenic activity, See Jobling, S., et al., “Detergent Components in Sewage Effluent are Weakly Estrogenic to Fish: An In-Vitro Study Using Rainbow Trout Hepatocytes,” Aquatic Toxicology, Vol. 27 (1993) pp. 361-372 and Soto, A. M. et al., “p-Nonylphenol: An Estrogenic Xenobiotic Released from Modified Polystyrene,” Env. Health Perspectives, Vol. 92 (1991) pp. 167-173. There is even concern with other traditionally used alkylphenols such as 2,4-dibutylphenol. See The Ministry of Heath, Labour and Welfare, Japan 2001, Chemical Substance Toxicity Test Report, 2,4 Di-tert-butylphenol, Vol 8 (1) 363-395.
Therefore, it is desirable to provide phosphites with lower contents of nonylphenol and which are not based on lower alkylphenols, especially 2,4-di-t-butylphenol. In the prior art, tris(nonylphenyl)phosphite has been made more hydrolytically stable by the addition of amines such as tris(isopropanol) amine (“TiPA”). Both tris(nonylphenyl)phosphite and tris(isopropanol) amine are FDA sanctioned for use in many polymer applications. U.S. Pat. Nos. 7,199,170 and 7,468,410 disclose phosphites that can replace TNPP but are either based on 2,4-di-t-butylphenol or lower alkylphenols. Any new phosphites which are to be considered as TNPP replacements need to be a liquid at room temperature and meet or exceed all the performance properties of TNPP. Important performance properties required include: good polymer compatibility, low odor in the polymer during processing, good melt flow and color stability in multi extrusion test, and good color stability in gas fade aging.
Therefore, it would be very desirable to produce a phosphite which does not suffer from the above drawbacks and yet maintains the performance characteristics of TNPP.